The present invention relates generally to aspheric cylindrical lens for collimating, with low optical aberrations, diode laser outputs and its method of fabrication and more particularly to aspheric cylindrical lens whereby a plurality of said lenses are fabricated from a master lens element by means of drawing the master lens element into the smaller aspheric cylindrical lenses.
Diode lasers are currently utilized in many applications. Many of these applications require a collimated diode laser output with low optical aberrations, however, diode lasers typically produce asymmetrically diverging output beams. In many instances, this asymmetric divergence may be quite fast, such as an 80.degree. output fan or larger, from the individual diode laser.
There have been a variety of proposed optical design solutions to collimate, with low optical aberrations, the asymmetric divergence of the output beam of diode lasers. One proposed solution is to mold plastic or glass aspheric optical elements in the shape desired in order to collimate the diverging output beam. An example of such a molded glass optical element is discussed in "Precision Molded-Glass Optics," written by R. Maschmeyer, et al. in Applied Optics, Volume 22, No. 6, on page 2410 in 1983. The glass optic elements which have been molded are generally limited in their ability to collimate a divergent output beam, however, due to stresses inherent in the glass element from the molding process. Additionally, molded plastic optical elements, while easier to mold than the relatively difficult to mold glass elements, tend to deform when subjected to high temperatures. Such deformation limits the plastic elements ability to collimate diode laser's output since high temperatures would often be experienced when the optical element was placed adjacent to the emitting facet of the diode laser.
An alternative method of collimating a divergent output from a diode laser involves the use of gradient index (GRIN) lenses such as the lens described in U.S. Pat. No. 4,668,053 which issued to Hissmi Nishi, et al. on May 26, 1987. While such GRIN lenses may be capable of collimating a divergent wavefront, their manufacture is typically complex. This complexity is due to the traditional methods of producing a GRIN lens by either chemical leaching of a glass rod, such that the refractive index is varied along the radius of the rod, or chemical vapor deposition of layers of particles having varied refractive indices, such that there is a concentric variation in the rod's refractive index. Thus, due to the typically complex methods for fabricating a GRIN lens, the utilization of such lenses is somewhat limited since they are quite expensive and require a sophisticated manufacturing process.
A third type of optical element for collimating a divergent output is a diffraction-based, computer-generated binary optical element as illustrated in U.S. Pat. No. 4,895,790 (hereinafter the '790 patent) which issued to Gary J. Swanson, et al. on Jan. 23, 1990. Binary optics, such as those in the '790 patent, have been able to collimate divergent wavefronts, however, the spatial resolution required of such optics has proved difficult to manufacture at a level high enough that a single binary optical element could collimate the diverging wavefront. Thus, a combination of binary and conventional refractive optical elements have typically been utilized to collimate the diverging wavefront resulting in the difficult alignment problems inherent when using a plurality of optical elements. Furthermore, the fabrication process for such binary optics is somewhat complex so that the binary optical elements produced are generally expensive.
Therefore it would be desirable to provide an optical element which is capable of collimating, with low optical aberrations, a highly divergent wavefront. Furthermore, it would be desirable if such collimating optical elements could be fabricated by a process which is relatively inexpensive and capable of mass producing such optical elements.